Fiber optic receptacle and plug assemblies

ABSTRACT

A fiber optic receptacle and plug assembly includes a receptacle adapted to be mounted within a wall of an enclosure and a plug mounted upon a fiber optic cable. The receptacle and the plug are provided with mating keys that permit the receptacle to receive only a plug of like ferrule configuration. The plug includes an adapter sleeve operable for receiving and optically connecting at least one plug ferrule and at least one receptacle ferrule when the plug is inserted into the receptacle. The receptacle is configured for use in a small volume enclosure requiring a minimal receptacle penetration depth. The receptacle is provided with a shoulder that engages the interior surface of the wall of the enclosure to provide strain relief against tensile pulling forces of up to about 600 lb/ft. The receptacle is provided with a dust cap and the plug is provided with a dust/pulling cap.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to fiber optic receptacle and plug assemblies for interconnecting optical fibers, and more specifically, to hardened fiber optic receptacle and plug assemblies including optical connectors and alignment features for interconnecting optical fibers at outside plant connection terminals in a fiber optic communications network.

2. Description of the Related Art

Optical fiber is increasingly being used for a variety of broadband applications including voice, video and data transmissions. As a result, fiber optic networks must include an ever-increasing number of interconnection points in which one or more of the optical fibers are interconnected or mated. For example, fiber optic networks may include a number of connection terminals, examples of which include, but are not limited to, distribution enclosures, network access point (NAP) enclosures, aerial closures, below grade closures, pedestals and network interface devices (NIDs). These various types of connection terminals provide protection, such as from moisture or other forms of environmental degradation, for the optical fibers and, more particularly, for the point at which the optical fibers are accessed from a fiber optic cable and optically connected. These various types of connection terminals may be used to provide services to an end user, commonly referred to as a subscriber. In this regard, fiber optic networks are being developed that deliver “fiber-to-the-curb” (FTTC), “fiber-to-the-business” (FTTB), “fiber-to-the-home” (FTTH) and “fiber-to-the-premises” (FTTP), referred to generically as “FTTx.”

In order to reduce installation labor costs in FTTx networks, communications service providers are increasingly demanding factory-prepared interconnection solutions, commonly referred to as “plug-and-play” systems. In the current development of plug-and-play systems, connection terminals are provided at distribution and interconnection points to establish optical connections between optical fibers accessed from a distribution cable (also referred to herein as “terminated”) and respective optical fibers of one or more drop cables, extended distribution cables or branch cables. Via these connection terminals, one or more terminated optical fibers are interconnected with one or more optical fibers of an extended distribution cable, branch cable or drop cable, collectively referred to herein as a “drop cable.” Regardless of the type of connection terminal and cable provided at the interconnection point, the connection terminal must include at least one opening through a wall, typically an external wall, operable for receiving one or more drop cables. At these openings, referred to herein as connector ports, assemblies for readily performing optical connections are needed. The assemblies should also protect the optical connections (i.e., connectors, adapter sleeves, ferrules, etc.) at which the optical fibers are interconnected against adverse environmental conditions, such as from water intrusion, and from mechanical influences, such as tensile forces (i.e., pulling forces generated during installation or by cable sag or wind or ice loading).

Conventional connector ports receive fiber optic receptacles in which one or more optical fibers of a drop cable are connected to respective optical fibers accessed within the enclosure. The optical fibers within the enclosure may be terminated directly to the receptacle or may be connectorized and terminated to the receptacle. In the past, these receptacles have been rather large in size because the enclosures in which they are held do not require minimal receptacle depths. Without significant depth restrictions, conventional receptacles include a receptacle housing defining an internal cavity that houses a receptacle adapter sleeve, also referred to herein as a “connector sleeve” or “connector adapter sleeve.” The adapter sleeve is designed to receive a pair of ferrules, each of which is mounted upon the end portions of one or more optical fibers. One of the ferrules is attached to the end portions of one or more optical fibers extending from a cable, ribbon or optical fiber device that extends into or is located in the interior of the enclosure. The other ferrule is mounted upon the end portions of one or more optical fibers extending from a cable, ribbon, or optical fiber device that extends outside or is located outside of the enclosure, such as the optical fibers of a fiber optic drop cable. The adapter sleeve assents in gross alignment of the ferrules, and ferrule guide pins or other alignment means assent in detailed alignment of the optical fibers on the opposing end faces of the ferrules.

In order to mate with a receptacle provided on a conventional connection terminal, a fiber optic plug is mounted upon the end portions of one or more optical fibers of the fiber optic drop cable. Typically, the plug includes a generally cylindrical plug body and a fiber optic connector including a connector and/or a plug ferrule disposed within the cylindrical plug body. In order to protect the plug ferrule, the cylindrical plug body may partially or completely surround the lateral sides of the fiber optic connector. The end of the cylindrical plug body is open such that the end face of the ferrule is accessible. The ferrule is mounted upon the end portions of the one or more optical fibers of the fiber optic drop cable such that mating the plug with the receptacle will align and optically connect the optical fibers of the fiber optic drop cable with respective optical fibers accessed within the connection terminal and terminated to the receptacle.

In the process of mating the plug and the receptacle, the plug ferrule is inserted into one end of the adapter sleeve housed within the receptacle. The adapter sleeve therefore aligns the plug ferrule with a receptacle ferrule that is attached to the end portions of the one or more optical fibers of the fiber optic cable, ribbon, or optical fiber device that extends into or is located within the interior of the connection terminal. As a result of the construction of a conventional fiber optic plug, the adapter sleeve is minimally received within the open end of the plug body as the plug ferrule is inserted into the receptacle. In addition, in order to retain the plug ferrule within the adapter sleeve, the connector of the fiber optic plug and the connector of the receptacle are mechanically coupled.

Several different types of conventional fiber optic connectors have been developed, examples of which include, but are not limited to, SC, LC, DC, MTP, MT-RJ and SC-DC connectors. The size and shape of each of these conventional connectors are somewhat different. Correspondingly, the size and shape of the adapter sleeve, the receptacle and the plug are also different. As such, according to conventional practice, different fiber optic receptacles are generally utilized in conjunction with the different types of fiber optic connectors. In this regard, the fiber optic receptacles generally define different sized internal cavities corresponding to the sizes of the adapter sleeve and, in turn, according to a ferrule of the fiber optic connector to be inserted within the adapter sleeve. Accordingly, a field service technician typically has to maintain several different types of fiber optic receptacles in inventory so that the proper type of receptacle can be installed depending upon the type of fiber optic connector to be inserted into the receptacle. Obviously, maintaining a number of different types of fiber optic receptacles in inventory is not only difficult for the technician to manage, but also increases the overall costs associated with maintaining a sufficient inventory.

In addition to using different types of fiber optic receptacles and/or plugs based upon the particular optical connector utilized, conventional receptacle/plug combinations are relatively large in size. Smaller and more space optimized assemblies are needed for low form factor and high density applications. Current smaller designs, however, are not dimensioned for the high tensile loads typically specified for “FTTx” applications (up to about 600 lb/ft). Contamination of the receptacle ferrule is also a significant issue, since many FTTx applications require that receptacles may remain unoccupied (i.e., not mated with a plug) for an extensive amount of time. Based on the need for increased loads and contamination prevention, it would be desirable to produce a small form factor, hardened fiber optic receptacle and mating plug adapted for mounting in a connection terminal defining an external wall through which optical fibers are interconnected. As yet, however, there is an unresolved need for a small form factor, hardened fiber optic receptacle that can receive a mating fiber optic plug utilizing various types of optical fiber connectors. There is a further unresolved need for a fiber optic receptacle and plug assembly defining an internal structure adapted to accommodate various types of optical connectors, and a hardened outer structure that provides superior resistance against tensile forces and superior contamination protection against adverse environmental conditions.

BRIEF SUMMARY OF THE INVENTION

To achieve the foregoing and other objects, and in accordance with the purposes of the invention as embodied and broadly described herein, the present invention provides various embodiments of fiber optic receptacle and plug assemblies, and more particularly, fiber optic receptacles and corresponding plugs of like optical connector configuration. Thus, the present invention provides fiber optic receptacle and plug assemblies designed to readily mate various types of optical connectors via the use of a connector port provided in a wall of a connection terminal. The present invention further provides a low form factor fiber optic receptacle and plug assembly adapted to be secured within a connector port of a connection terminal, while providing strain relief against tensile forces of up to about 600 lb/ft and protection against adverse environmental conditions.

In an exemplary embodiment, the present invention provides a fiber optic receptacle and plug assembly comprising a fiber optic receptacle adapted to be secured within a connector port of a connection terminal and a corresponding fiber optic plug mounted upon the end portions of one or more optical fibers of a fiber optic cable. The fiber optic receptacle and the fiber optic plug comprise keyed designs that allow the fiber optic receptacle to receive only a fiber optic plug of like ferrule configuration. The fiber optic plug engages a corresponding receptacle positioned within a connector port provided in an external wall or an internal wall of a connection terminal or other enclosure. The keyed design of the fiber optic receptacle and plug assembly allows non-centric positions of at least one ferrule and includes keys for radial alignment of the at least one ferrule. The fiber optic plug comprises an adapter sleeve operable for receiving and optically connecting at least one plug ferrule and at least one receptacle ferrule, thus minimizing the depth of the receptacle portion of the assembly. The fiber optic receptacle comprises a shoulder that is secured against a wall of the connection terminal in order to provide strain relief against tensile forces of up to about 600 lb/ft. A receptacle boot allows the assembly to be installed in a breathable enclosure.

In another embodiment, the present invention provides a fiber optic receptacle and plug assembly comprising a fiber optic receptacle adapted to be secured within a connector port of a connection terminal. The fiber optic receptacle comprises a receptacle housing defining an internal cavity opening through opposed first and second ends, wherein the internal cavity is operable for receiving an adapter sleeve of a corresponding fiber optic plug through the first end. The receptacle housing further defines a shoulder that is secured against an interior surface of the wall operable for providing strain relief against tensile forces of up to about 600 lb/ft. At least one receptacle ferrule is disposed and mounted within the internal cavity via a ferrule retainer disposed proximate the second end. The assembly further comprises a fiber optic plug comprising a plug inner housing, a plug outer housing, a coupling nut, at least one plug ferrule and an adapter sleeve operable for receiving and optically connecting the at least one plug ferrule and the at least one receptacle ferrule. The fiber optic receptacle and the fiber optic plug comprise keyed designs that allow the fiber optic receptacle to properly receive only a fiber optic plug of like ferrule configuration. The receptacle may further comprise a bias member that operably engages the ferrule retainer to urge the at least one receptacle ferrule toward the first end of the receptacle housing.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the present invention are better understood when the following detailed description of the invention is read with reference to the accompanying drawings, in which:

FIG. 1 is an exploded perspective view of a single ferrule (i.e., simplex) version of a fiber optic receptacle and plug assembly in accordance with an exemplary embodiment of the present invention shown with the receptacle and plug disengaged and with the protective dust/pulling caps of the receptacle and plug removed;

FIG. 2 is a perspective view of the fiber optic receptacle and plug assembly of FIG. 1 shown with the plug engaging the receptacle;

FIG. 3 is an exploded perspective view of the fiber optic receptacle of FIG. 1 showing the receptacle body, the receptacle ferrule, the ferrule retainer, the protective end cap and the receptacle seal boot;

FIG. 4 is a cross-sectional view of the fiber optic receptacle of FIG. 3 shown in its assembled configuration;

FIG. 5 is an exploded perspective view of the fiber optic plug of FIG. 1 showing the plug body, the plug ferrule, the adapter sleeve, the protective end/pulling cap, the crimp band and the coupling nut;

FIG. 6 is a cross-sectional view of the fiber optic plug of FIG. 5 shown in its assembled configuration;

FIG. 7 is an exploded perspective view of a dual ferrule (i.e., duplex) version of a fiber optic receptacle and plug assembly in accordance with another exemplary embodiment of the present invention shown with the receptacle and plug disengaged and with the protective dust/pulling caps of the receptacle and plug removed;

FIG. 8 is a perspective view of the fiber optic receptacle and plug assembly of FIG. 7 shown with the plug engaging the receptacle;

FIG. 9 is an exploded perspective view of the fiber optic receptacle of FIG. 7 showing the receptacle body, two receptacle ferrules, the ferrule retainer, the protective end cap and the receptacle seal boot;

FIG. 10 is a cross-sectional view of the fiber optic receptacle of FIG. 9 shown in its assembled configuration;

FIG. 11 is an exploded perspective view of the fiber optic plug of FIG. 7 showing the plug body, two plug ferrules, the adapter sleeve, the protective end/pulling cap, the crimp band and the coupling nut; and

FIG. 12 is a cross-sectional view of the fiber optic plug of FIG. 11 in its assembled configuration.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which exemplary embodiments of the invention are shown. However, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These exemplary embodiments are provided so that this disclosure will be both thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numbers refer to like elements throughout the various drawings.

In the various embodiments described below, the present invention comprises fiber optic receptacle and plug assemblies including one or more optical connectors or ferrules for interconnecting optical fibers within a communications network. The receptacle portion of each assembly is adapted to be mounted within a wall of an enclosure or similar structure, such as a network distribution or interconnection terminal, through which one or more optical fibers of a fiber optic cable are routed. A rigid shoulder of the fiber optic receptacle is mounted against the wall of the enclosure, thus providing superior retention for external tensile forces as compared to conventional threaded designs that use a nut on the inside of the wall for securing the receptacle. In the exemplary embodiments shown and described herein, the fiber optic plug portion of each assembly includes a fiber optic cable comprising one or more optical fibers for optically connecting a corresponding plurality of optical fibers received within the receptacle portion. As used herein, the fiber optic cable associated with the plug portion is referred to as the “drop cable” and is intended to include all types of fiber optic cables such as, but not limited to, a branch cable, a distribution cable, an extended distribution cable, a flat dielectric drop cable, a figure-eight drop cable or an armored drop cable. The drop cable typically comprises between one and about twelve optical fibers, but may comprise up to about 24 fibers depending on the construction of the drop cable and the number and type of optical connectors. Furthermore, the particular components of the fiber optic receptacle and plug assemblies described herein may be modified to accommodate different cable and optical connector types.

In all embodiments shown and described herein, different types of fiber optic cables may function as the drop cable such as, but not limited to, monotube, loose tube, central tube, ribbon, flat dielectric and the like. However, in the exemplary embodiments shown, the drop cable comprises a cable jacket, a strength component and an optical transmission component disposed within the cable jacket. In one embodiment, the strength component comprises two glass-reinforced plastic (GRP) strength components and the optical transmission component comprises an optical waveguide disposed within a central buffer tube. The drop cable may also comprise strength members that provide additional tensile strength. As used herein, the term “strength component” refers to a strength element having anti-buckling strength, while the term “strength member” refers to a strength element lacking anti-buckling strength. Furthermore, the term “tensile element” refers generically to either a strength component or a strength member. Strength members allow a fiber optic cable to have a smaller cross-sectional footprint due to the fact that they allow the strength components to have smaller diameters since they will not provide all of the tensile strength to the cable. In other words, the strength components and the strength members combine to carry the tensile load. Moreover, by using strength members, the cable remains relatively flexible and is easier to handle. It is understood that other cable types may be used in conjunction with the present invention. Moreover, various optical connectors may be used with different fiber optic cables according to the concepts of the present invention, thereby resulting in numerous cable/connector combinations. The drop cable is preferably designed to provide stable performance over a wide range of temperatures and to be compatible with any telecommunications grade optical fiber. As used herein, the term “optical fiber” is intended to include all types of single mode and multi-mode light waveguides, including one or more bare optical fibers, coated optical fibers, loose-tube optical fibers, tight-buffered optical fibers, ribbonized optical fibers or any other expedient for transmitting light signals.

The fiber optic connector and plug assemblies of the present invention provide a hardened, fully-sealed configuration that prevents adverse environmental conditions, such as moisture and contamination, from reaching the end faces of the optical fibers and the ferrules. In all the exemplary embodiments shown herein, O-rings provide static seals, and their position combined with relief features minimize vacuum build-up when removing the plug from the receptacle and pressure build-up when mating the plug with the receptacle. Generally speaking, most of the components of the receptacle and plug are formed from a suitable polymer. Preferably, the polymer is a UV stabilized polymer such as VECTRA® A130 liquid crystal polymer (LCP) available from Celanese AG Ticona of Summit, N.J. or ULTEM® 2210 available from General Electric Plastics Company of Pittsfield, Mass. However, other suitable materials may also be used. For example, stainless steel or any other non-corrosive or coated metal may be used for various components.

Referring now to FIGS. 1-6, a fiber optic receptacle and plug assembly according to one embodiment of the present invention is shown. The assembly includes a fiber optic receptacle 20 and a corresponding fiber optic plug 22. The receptacle 20 is typically mounted within a connector port (not shown) provided in an external wall or an internal wall, referred to hereinafter as a “wall,” of a distribution or interconnection enclosure, such as a connection terminal in a fiber optic communications network. The receptacle 20 is operable for connecting one or more optical fibers outside of the wall with one or more optical fibers within the enclosure. It should be understood, however, that the fiber optic receptacle 20 may be mounted to other structures, for example to a connector panel, patch panel or similar substantially planar surface, without departing for the intended scope of the invention. Each such connector port is operable for receiving a receptacle 20 and at least one connectorized optical fiber on the inside of the connector port, and the plug 22 and at least one connectorized optical fiber of a drop cable 24 on the outside of the connector port. The plug 22 is mounted upon the end portion of the drop cable 24 and is adapted to mate with the corresponding receptacle 20. The receptacle 20 and plug 22 are operable for aligning and maintaining the opposing optical fibers in contact. A single connector port may accommodate more than one optical fiber of the drop cable 24, either by receiving a multifiber ferrule or by receiving multiple single-fiber ferrules within the receptacle 20.

Referring specifically to FIG. 1, the receptacle 20 and the corresponding plug 22 are shown disengaged from one another and with their respective dust caps 28, 34 removed. A threaded coupling nut 26 of the plug portion of the assembly, operable for securing the plug 22 to the receptacle 20 upon engagement, may be used to secure the protective dust cap 28 during installation. The dust cap 28 defines a threaded portion 29 at its rearward end and a pulling grip 30 at its forward end. The dust cap 28 protects the optical connector 32 of the plug 22 during installation and until engagement with the receptacle 20. When removed, the dust cap 28 may be secured to the drop cable 24 using a tether 33, and may be reused if the plug 22 is disengaged from the receptacle 20 at a later time. In preferred embodiments, the pulling grip 30 should be able to withstand pulling forces up to about 600 lb/ft. The pulling grip 30 and the dust cap 28 have a generally rounded forward end to facilitate installation through ducts or around pulleys. As with the plug portion of the assembly, the receptacle portion may also be covered and sealed with a threaded dust cap 34 that is removed prior to inserting the plug 22. The receptacle dust cap 34 may also be secured to the receptacle 20 using a tether 33. At the end of the receptacle 20 opposite the threaded portion, a boot 36 protects the receptacle 20, and in some embodiments may also provide sealing. The protective boot 36 allows the receptacle 20 to be installed in a breathable enclosure and may be unnecessary if the receptacle 20 is otherwise reliably sealed from the environment.

Referring specifically to FIG. 2, the plug 22 is mounted upon the end portion of the fiber optic drop cable 24 and is adapted to mate with the corresponding receptacle 20. To secure the plug 22 and receptacle 20 together, the coupling nut 26 engages the threaded end of the receptacle 20. The features that secure the assembly within the connector port of the wall of the enclosure will be described below.

Referring now to FIG. 3, the fiber optic receptacle 20 includes a receptacle housing 38 operable for mounting the receptacle 20 to the wall of the enclosure, holding a ferrule assembly and aligning both the receptacle ferrule assembly and the fiber optic plug 22 so that they engage one another in only one preferred orientation. This feature is advantageous for orientation critical applications including angled physical contact (APC) type ferrules where minimal angular offset is permissible, as well as multi-fiber ferrules that often are not centric. The receptacle housing 38 defines an internal cavity 40 opening through opposed first end 42 and second end 44. Typically, the size of the opening 40 through the first end 42 is relatively large so as to receive the corresponding fiber optic plug 22. Conversely, the size of the opening through the second end 44 is typically smaller and, in one advantageous embodiment, is sized to be only slightly larger than the receptacle ferrule 46, such that the receptacle ferrule 46 can be inserted, but is received through the opening 40 in a slight loose fit. The relatively large size of the opening 40 at the first end 42 allows the end face of the receptacle ferrule 46 to be cleaned with a Q-tip or special tool. This is advantageous since the receptacle 20, in contrast to the fiber optic plug 22, may be exposed to weather when not used for a prolonged period of time and may collect contamination. This embodiment allows for easy cleaning and improved access without disassembly of the ferrule receptacle 46 from the receptacle housing 38.

Although the fiber optic receptacle 20 may house a variety of fiber optic connector types including LC, MTRJ, MTP, SC-DC, and the like, the receptacle 20 shown in FIGS. 1-6 houses, by way of example and not by way of limitation, a single ferrule assembly of the type utilized in a conventional SC type connector. Although not included in this particular embodiment, the fiber optic receptacle 20 may also include an adapter sleeve disposed within the internal cavity 40 defined by the receptacle housing 38. If present, the adapter sleeve may have a sleeve member that defines a lengthwise extending passageway having opposed ends for receiving and aligning a plug ferrule (not shown) with the receptacle ferrule 46. In this regard, the plug ferrule of the fiber optic plug 22 may be inserted into one end of the adapter sleeve, while the receptacle ferrule 46 that is mounted upon the ends of optical fibers extending through the enclosure may be inserted through the opening defined by the second end 44 of the receptacle 20 and into the other end of the adapter sleeve. In this embodiment, however, the adapter sleeve is a component of the plug 22 and is inserted into the internal cavity 40 of the receptacle 20 upon mating the plug 22 with the receptacle 20.

The receptacle housing 38 in the embodiment shown is cylindrically shaped and defines a shoulder portion 48 positioned medially about midway between the first end 42 and the second end 44. Upon installation within a connector port of a wall, the first end 42 of the receptacle housing 38 is inserted through the connector port from the inside of the wall until the surface of the shoulder portion 48 proximate the first end 42 comes into contact with the interior surface of the wall. By securing the receptacle 20 within the wall using the shoulder 48, as opposed to a nut, the receptacle 20 provides strain relief against tensile forces of up to about 600 lb/ft. A seal may be provided between the receptacle housing 38 and the interior surface of the wall using a conventional O-ring seal (not shown), multi-point seal 50 or like sealing means. The receptacle housing 38 defines a groove 52 for receiving the multi-point seal 50. The groove 52 may further receive a crescent ring 54 for retaining the multi-point seal 50 in place and securing the receptacle 20 within the connector port. The coupling nut 26 of the plug 22 is used to further secure the receptacle 20 within the connector port.

The fiber optic receptacle 20 also preferably includes a ferrule retainer 56 operable for retaining the receptacle ferrule 46 within the internal cavity 40 of the receptacle housing 38. The ferrule retainer 56 and the receptacle housing 38 can be connected in various manners, but, in one advantageous embodiment, the ferrule retainer 56 includes hooks 58 that are received by features 60 that project outwardly from the receptacle housing 38. The ferrule retainer 56 can be removed from the receptacle housing 38 in order to access the receptacle ferrule 46, such as for cleaning, repair or replacement. The design of the ferrule retainer 56 allows for easy removal without a tool at any point in time. Once the receptacle ferrule 46 has been cleaned, repaired or replaced, the receptacle ferrule 46 can be reinserted into the opening 40 of the receptacle housing 38 and the ferrule retainer 56 can be reconnected to the receptacle housing 38.

The fiber optic receptacle 20 of this particular embodiment also includes a bias member disposed within the receptacle housing 38. The bias member is disposed between and operably engages the ferrule retainer 56 and the receptacle ferrule 46 to urge the receptacle ferrule toward the first end 42 of the receptacle housing 38. Typically, the bias member is one or more linear coil springs 62 as shown. Thus, the receptacle ferrule 46 is biased towards the first end 42 of the receptacle housing 38, but is allowed to move relatively freely within the opening 40 and the adapter sleeve (not shown) of the plug 22, thus allowing a compressive force to seat the receptacle ferrule 46 against the mating plug ferrule (not shown). The boot 36 rests against the shoulder portion 48 of the receptacle housing 38 and protects the components of the receptacle 20 positioned adjacent the interior surface of the wall of the enclosure. The boot 36 defines an opening 64 for receiving the fiber optic cable (not shown) and/or optical fibers (not shown) from within the enclosure.

FIG. 4 is a cross-section of the assembled receptacle 20 taken along line A-A of FIG. 3, the same or similar parts being identified by like reference numerals. An O-ring 66 may be used to provide a seal between the dust cap 34 and the receptacle housing 38. As is shown in FIG. 4, the multi-point seal 50 is retained within the groove of the receptacle housing 38 and provides sealing points between the receptacle housing 38 and the wall (not shown) of the enclosure. The wall is positioned between the shoulder portion 48 of the receptacle housing 38 and the crescent ring 54 with the shoulder portion 48 engaging the interior surface of the wall. In one embodiment, the crescent ring 54 secures the receptacle 20 in place. In an alternative embodiment, the dust cap 34 or the coupling nut 26 of the plug 22 is used to secure the receptacle 20 in place.

Referring to FIG. 5, the fiber optic plug 22 comprises a plug ferrule 70, an inner housing 72 with a crimp, an adapter sleeve 74, an outer housing 68 and a coupling nut 26. There is also a molded-on plug boot (not shown) made of a flexible (silicone-type or other like) material secured over a portion of the outer housing 68 and a portion of the drop cable 24 in order to seal the exposed portion of the drop cable 24 and generally inhibit kinking while providing bending strain relief to the cable 24 near the plug 22. The strength components 78 are terminated on the inner housing 72 and a crimp band 80 is secured around the strength components 78. The crimp band 80 is preferably made from brass, but other suitable deformable materials may be used. The strength members (not shown) are cut flush with the stripped-back jacket 76, thereby exposing the two GRP strength components 78 and optical component 82 adjacent the end of the cable 24. The crimp band 80 provides strain relief for the cable 24. The inner housing 72 is assembled by first crimping the crimp band 80 to the strength components 78 of the cable 24. The outer housing 68 is then slid over the inner housing 72. As is well known ad understood in the art, the outer housing 68 is threaded onto the cable 24 before the cable 24 is crimped to the inner housing 72. The adapter sleeve 74 secures the fit of the parts and allows the plug 22 to be disassembled in a reverse manner.

The plug ferrule 70 extends lengthwise and is at least partially disposed within the inner housing 72. The plug ferrule 70 may therefore be mounted within the inner housing 72 such that the front face of the plug ferrule 70 extends somewhat beyond the forward end of the inner housing 72. As with the corresponding fiber optic receptacle 20, the plug 22 may house a variety of fiber optic connector types including LC, MTRJ, MTP, SC-DC, and the like. However, the plug 22 of the particular embodiment shown houses a single ferrule assembly of the type utilized in a conventional SC type connector because the receptacle 20 can only receive a plug 22 of like ferrule configuration. The plug ferrule 70 is received within the lengthwise passageway defined by the adapter sleeve 74 for mating the plug ferrule 70 and the receptacle ferrule 46. As stated above, the adapter sleeve 74 may be a component of either the receptacle 20 or the plug 22. As shown, the adapter sleeve 74 is a component of the plug 22 so as to minimize the overall size of the receptacle 20, thereby providing a small form factor receptacle.

The outer housing 68 has a generally cylindrical shape with a forward first end 84 and a rearward second end 86. The outer housing 68 generally protects the inner housing 72 and in preferred embodiments also keys engagement of the plug 22 with the mating receptacle 20. Moreover, the inner housing 68 includes a through passageway between the first and second ends 84 and 86. The passageway of the inner housing 72 is keyed so that the inner housing 72 is inhibited from rotating when the plug 22 is assembled. The first end 84 of the outer housing 68 includes a keyed opening 88 defined by the housing 68 for aligning the plug 22 with the receptacle 20 for radial alignment of the plug ferrule 70 with the receptacle ferrule 46. The plug 22 and the corresponding receptacle 20 are shaped to permit mating in only one orientation. In preferred embodiments, this orientation may be marked on the receptacle 20 and on the plug 22 using alignment indicia so that a field technician can readily mate the plug 22 with the receptacle 20 even when the internal components of the fiber optic receptacle and plug assembly are not visible. Any suitable indicia may be used. After alignment, the field technician engages the internal threads of the coupling nut 26 with the external threads of the receptacle 20 to secure the plug 22 to the receptacle 20.

The outer housing 68 may further define a shoulder 90 that provides a mechanical stop for both an O-ring 92 disposed on the outer housing 68 and the coupling nut 26. The O-ring 92 provides a weatherproof seal between the plug 22 and the receptacle 20. The coupling nut 26 has a passageway sized so that it fits over the second end 86 of the outer housing 68 and easily rotates about the medial portion of the outer housing 68. In other words, the coupling nut 26 cannot move beyond the shoulder 90, but is able to rotate with respect to the outer housing 68. FIG. 6 is a cross-section of the assembled plug 22 taken along line B-B of FIG. 5, the same or similar parts being identified by like reference numerals.

Referring to FIG. 7, a dual ferrule (i.e., duplex) version of a fiber optic receptacle and plug assembly is shown. In this embodiment, the drop cable is not shown, however, it is understood that the drop cable may include a branch cable, distribution cable, extended distribution cable, flat dielectric drop cable, figure-eight drop cable or an armored drop cable comprising two or more optical waveguides. As with the embodiment shown in FIGS. 1-6, the receptacle 20 is mounted within a connector port of a wall of an enclosure, such as a network connection terminal. The plug 22 is aligned with and engages only a receptacle 20 of like optical connector configuration. The plug 22 shown allows a single receptacle 20 to accommodate more than one optical fiber accessed and connectorized for optical connection within the connection terminal. At the same time, the drop cable associated with the plug 22 is strain relieved at the connector port.

The receptacle 20 and the corresponding plug 22 are shown disengaged and with their respective dust caps 34, 28 removed. A threaded coupling nut 26 of the plug portion of the assembly, operable for securing the plug 22 to the receptacle 20 upon engagement, may be used to secure the protective dust cap 28 during installation. A protective boot 36 allows the fiber optic receptacle 20 to be installed in a breathable enclosure and may be unnecessary if the receptacle 20 is otherwise reliably sealed from adverse environmental conditions. As in the previous embodiment, the outer housing 68 of the plug 22 has a generally cylindrical shape and keys engagement of the plug 22 with the mating receptacle 20. The outer housing 68 defines an alignment feature 94, which has a specific shape so that the plug 22 and receptacle 20 mate in only one orientation. In preferred embodiments, this orientation may be marked on both the outer housing 68 and the receptacle housing 38 using alignment indicia so that a field technician can readily mate the plug 22 with the receptacle 20 even when the internal components of the receptacle 20 and plug 22 are not visible. The alignment indicia on the plug 22 is aligned with the complimentary alignment indicia disposed on the receptacle 20. Thereafter, the field technician engages the internal threads of the coupling nut 26 with the external threads of the receptacle 20 to secure the plug 22 to the receptacle 20.

Referring to FIG. 8, the fiber optic plug 22 may be mounted upon any suitable fiber optic drop cable including more than one optical fiber since the optical connector shown includes more than one ferrule, such as two LC ferrules. To secure the plug 22 to the receptacle 20, the coupling nut 26 engages the threaded end of the receptacle 20. The plug 22 may be secured in the field without special tools, equipment or training. Additionally, the physical connection may be easily connected or disconnected by merely mating or un-mating the plug 22 with the receptacle 20 and engaging or disengaging threads of the coupling nut 26 with the threads of the receptacle 20. Thus, the receptacle/plug assembly of the present invention allows the deployment of multiple optical fibers, through a connector port provided in a wall of a conventional network connection terminal in an easy and economical manner. The concepts of the present invention may be practiced with other fiber optic cables, connectors and/or other cable configurations.

Referring to FIG. 9, as in the embodiment described above, the fiber optic receptacle 20 includes a receptacle housing 38 operable for mounting to a wall, holding a pair of receptacle ferrules and aligning both the internal receptacle ferrules with the fiber optic plug 22 so that they engage in only one preferred orientation. The receptacle housing 38 defines an internal cavity 40 opening through opposed ends, a first end 42 and a second end 44. The openings through the second end 44 are typically smaller and, in one advantageous embodiment, are sized to be only slightly larger than the receptacle ferrules 46, such that the receptacle ferrules 46 can be inserted, but are received through the openings in a slight loose fit. Although the fiber optic receptacle 20 may house a variety of fiber optic connector types including LC, MTRJ, MTP, SC-DC, and the like, the receptacle 20 shown in FIGS. 7-12 houses, by way of example and not by way of limitation, dual ferrule assemblies of the type utilized in a conventional LC type connector. As in the previous embodiment, the adapter sleeve 74 is a component of the plug 20 and is inserted into the internal cavity 40 of the receptacle 20 upon insertion of the plug 22 into the receptacle 20.

The receptacle housing 38 in the embodiment shown is cylindrically shaped and defines a shoulder portion 48 positioned medially about midway between the first end 42 and the second end 44. Upon installation within a wall of an enclosure, the first end 42 of the receptacle housing 38 is inserted through the connector port from the inside of the enclosure until the surface of the shoulder portion 48 proximate the first end 42 comes into contact with the interior surface of the wall. A seal is provided between the receptacle housing 38 and the wall using an O-ring (not shown), multi-point seal 50 or like sealing means. The receptacle 20 also includes a ferrule retainer 56 operable for retaining the receptacle ferrules 46 within the internal cavity 40 of the receptacle housing 38. The ferrule retainer 56 defines clips or hooks 58 that grip features 60 defined by the receptacle housing 38 for securing the ferrule retainer 56 to the receptacle housing 38. The ferrule retainer 56 can be removed from the receptacle housing 38 in order to access the receptacle ferrules 46, such as for cleaning, repair, replacement or the like.

The fiber optic receptacle 20 further includes bias members 62 that engage the ferrule retainer 56 to urge the receptacle ferrules 46 toward the first end 42 of the receptacle housing 38. Thus, the receptacle ferrules 46 are biased towards the first end 42 of the receptacle housing 38, but are allowed to move relatively freely within the opening 40 and the adapter sleeve (not shown) of the plug 22, thus allowing a compressive force to seat the receptacle ferrules 46 against the mating plug ferrules (not shown). It should be understood, however, that the fiber optic receptacle 20 can include other types of bias members 62, in addition to or instead of the one or more linear coil springs shown herein. The ferrule retainer 56 may also include one or more posts (not shown) extending in a lengthwise direction such that a spring can be mounted upon a respective post. In addition, each spring 62 would be longer than its respective post, even in the compressed state. As such, the posts serve to position the springs 62 that, in turn, contact the receptacle ferrules 46 and to provide additional lateral stability. FIG. 10 is a cross-section of the assembled plug 22 taken along line C-C of FIG. 9, the same or similar parts being identified by like reference numerals. A conventional sealing O-ring 66 may be disposed between the dust cap 34 and the receptacle housing 38. The fiber optic receptacle 20 is adapted to receive a corresponding fiber optic plug 22 when the plug ferrules 70 of the fiber optic plug 22 are aligned with and inserted into the first end 42 of the receptacle housing 38.

Referring to FIG. 11, the corresponding plug 22 for the receptacle 20 shown in FIGS. 9-10 generally includes a plug inner housing 72, plug ferrules 70, an adapter sleeve 74, an outer housing 68 and a coupling nut 26. There is also a molded-on plug boot (not shown) made of a flexible (silicone-type or other like) material secured over a portion of the outer housing 68 and a portion of the drop cable (not shown) in order to seal and provide bending strain relief to the cable near the plug 22. The crimp band 80 is secured around the strength components (not shown) of the cable and provides strain relief for the cable. The plug ferrules 70 extend lengthwise and are partially disposed within the inner housing 72. To match the corresponding receptacle 20, the fiber optic plug 22 may include a variety of fiber optic connector types including SC, LC, MTRJ, MTP, SC-DC, and the like. The plug 22 of the particular embodiment is shown to include dual LC ferrules which are smaller than SC connectors, thus allowing the overall diameter of the fiber optic receptacle and plug assembly to remain the same as the embodiment described above. The plug ferrules 70 are received within the lengthwise passageway defined by the adapter sleeve 74 that mates the plug ferrules 70 with the receptacle ferrules 46. The receptacle ferrules 46 are inserted into the forward end of the adapter sleeve 74. Thus, the adapter sleeve 74 serves to align the plug ferrules 70 inserted into the adapter sleeve 74 with the receptacle ferrules 46 inserted into the other end of the adapter sleeve 74. As such, the optical fibers upon which the opposing ferrules are mounted are correspondingly aligned and optically interconnected.

The outer housing 68 generally protects the inner housing 72, and in preferred embodiments, also keys engagement of the plug 22 with the mating receptacle 20. Moreover, the outer housing 68 includes a through passageway that is keyed so that the inner housing 72 is inhibited from rotating when the plug 22 is assembled. The outer housing 68 includes a keyed opening 88 for aligning the plug 22 with the receptacle 20 for radial alignment of the opposing ferrules. The plug 22 and the corresponding receptacle 20 are shaped to permit mating in only one orientation. In preferred embodiments, this orientation may be marked on the receptacle 20 and on the plug 22 using alignment indicia so that a field technician can readily mate the plug 22 with the receptacle 20. Any suitable indicia may be used. After alignment, the field technician engages the internal threads of the coupling nut 26 with the external threads of the receptacle 20 to secure the plug 22 to the receptacle 20.

The outer housing 68 may further define a shoulder 90 that provides a mechanical stop for both an O-ring 92 and the coupling nut 26. The O-ring 92 provides a weatherproof seal between the plug 22 and the receptacle 20. The coupling nut 26 has a passageway sized so that it fits over the end of the outer housing 68 and easily rotates about the medial portion of the outer housing 68. FIG. 12 is a cross-section of the assembled plug 22 taken along line C-C of FIG. 11, the same or similar parts being identified by like reference numerals.

In alternative embodiments, the coupling threads may be replaced with a bayonet style or a push-pull mechanism to hold the plug 22 within the receptacle 20. Alternatively, a clip may be added to engage the outer housing 68 of the plug 22 and the receptacle housing 38 of the receptacle 20 to hold them together. Sealing features may be relaxed or eliminated entirely based upon the particular application. The plug boot may be pre-manufactured and assembled, or may be overmolded as is known in the art. Further, heat deformable tubing may be used to fulfill the same purpose as the boot when aesthetics are less important and bend characteristics less stringent. As stated above, the adapter sleeve 74 may be integrated into the receptacle 20 instead of the plug 22 when the overall diameter of the receptacle 20 is not restricted, while maintaining the same assembly technique, allowing for easy removal for cleaning, repair and replacement.

Designs for several types of ferrules (including multi-fiber) can be derived from this base design relatively easily. Multi-ferrule designs driven by the available space and requirements are possible, such as MTP, MTRJ, DC, multiple 1.25 mm, multiple 2.5 mm, etc. Additional strain relief may be added to the receptacle 20 if needed. Crimping solutions may differ depending on the drop cable type and requirements. If the drop cable does not include the dual GRP dielectric strength members as shown in the first embodiment, the methods of coupling the strength member to the plug body may include glue or other means of fastening, such as clamps or cable ties.

The embodiments described above provide advantages over conventional fiber optic receptacle and plug assemblies. For example, the low form factor of the embodiments described above allows for their use in about a 38 mm diameter package for FTTx distribution cables and permits their use in enclosures requiring a very low receptacle penetration depth. One example of a low penetration depth application is described in co-pending U.S. patent application Ser. No. 10/855,179, filed May 27, 2004, entitled DISTRIBUTION CABLE HAVING ARTICULATED OPTICAL CONNECTOR NODES and assigned to the assignee of the present invention. The direct key alignment of these fiber optic receptacle and plug assemblies also makes them fully compatible with APC type ferrules, and the unique fit prevents assembly errors during production and installation. By locating the adapter sleeve 74 within the plug 22 as opposed to the receptacle 20 in the exemplary embodiments shown and described herein, the receptacle volume and overall diameter is reduced and the receptacle ferrule(s) may be readily accessed for cleaning, repair or replacement. The overmolded boot eliminates the need for heat shrinkable tubing and also improves the assembly's integrity under adverse environmental conditions in which a preformed boot may disengage.

The foregoing is a description of various embodiments of the invention that are given here by way of example only. Although fiber optic receptacle and plug assemblies have been described with reference to preferred embodiments and examples thereof, other embodiments and examples may perform similar functions and/or achieve similar results. All such equivalent embodiments and examples are within the spirit and scope of the present invention and are intended to be covered by the appended claims. 

1. A fiber optic receptacle and plug assembly, comprising: a receptacle adapted to be mounted within a wall of an enclosure, the receptacle comprising a ferrule retainer and at least one receptacle ferrule; and a plug mounted upon an end of a fiber optic cable, the plug comprising an adapter sleeve and at least one plug ferrule disposed within the adapter sleeve for mating with the receptacle ferrule when the plug is inserted into the receptacle; wherein the receptacle and the plug are keyed to permit the receptacle ferrule and the plug ferrule to be mated in only one orientation.
 2. The fiber optic receptacle and plug assembly of claim 1, wherein the at least one receptacle ferrule comprises a pair of single-fiber, small form factor ferrules and the at least one plug ferrule comprises a pair of single-fiber, small form factor ferrules of like configuration.
 3. The fiber optic receptacle and plug assembly of claim 1, wherein one of the receptacle and the plug comprises a key for radial alignment of the at least one receptacle ferrule relative to the at least one plug ferrule.
 4. The fiber optic receptacle and plug assembly of claim 1, wherein the plug further comprises an inner housing for receiving and strain relieving a fiber optic cable having at least one optical fiber and an outer housing disposed about the inner housing.
 5. The fiber optic receptacle and plug assembly of claim 1, wherein the receptacle comprises a shoulder adapted to engage an interior surface of the wall of the enclosure to provide stain relief against tensile forces of up to about 600 lb/ft when the plug is secured to the receptacle.
 6. The fiber optic receptacle and plug assembly of claim 1, wherein the receptacle comprises a receptacle boot that permits the receptacle to be installed in a breathable enclosure.
 7. The fiber optic receptacle and plug assembly of claim 1, wherein the plug further comprises an overmolded boot operable for sealing between the plug and a fiber optic cable.
 8. The fiber optic receptacle and plug assembly of claim 1, wherein the plug is secured to the receptacle by one of a threaded coupling nut, a bayonet-style connection and a push-pull mechanism.
 9. The fiber optic receptacle and plug assembly of claim 4, wherein the fiber optic cable is one of a branch cable, a distribution cable, an extended distribution cable, a flat dielectric drop cable, a figure-eight drop cable and an armored drop cable.
 10. The fiber optic receptacle and plug assembly of claim 1, wherein the at least one receptacle female and the at least one plug ferrule are selected from the group consisting of SC, LC, MTRJ, MTP, SC-DC connector type ferrules.
 11. A fiber optic receptacle and plug assembly, comprising: a receptacle adapted to be mounted within a wall of an enclosure, the receptacle comprising at least one receptacle ferrule for engaging at least one plug ferrule of like configuration when a corresponding plug is inserted into the receptacle, the receptacle further comprising: a receptacle housing defining an internal cavity opening through opposed first and second ends, the internal cavity operable for receiving the at least one plug ferrule through the first end of the receptacle housing and the at least one receptacle ferrule through the second end of the receptacle housing, the receptacle housing defining a radially extending shoulder for engaging an interior surface of the wall of the enclosure; and a ferrule retainer for positioning the at least one receptacle ferrule within the opening in the second end of the receptacle housing.
 12. The fiber optic receptacle and plug assembly of claim 11, wherein the receptacle housing has a peripheral groove medially disposed between the first and second ends for receiving a seal.
 13. The fiber optic receptacle and plug assembly of claim 11, wherein the receptacle housing comprises a feature for cooperating with a corresponding feature provided on the ferrule retainer for securing the ferrule retainer to the receptacle housing in a predetermined orientation.
 14. The fiber optic receptacle and plug assembly of claim 11, further comprising a biasing means disposed between the receptacle housing and the ferrule retainer such that the at least one receptacle ferrule is biased in the direction of the first end of the receptacle housing.
 15. The fiber optic receptacle and plug assembly of claim 11, wherein the shoulder is adapted to engage an interior surface of the wall of the enclosure to provide strain relief against tensile forces of up to about 600 lb/ft when the plug is secured to the receptacle.
 16. A fiber optic receptacle and plug assembly, comprising: a plug adapted for optically connecting at least one plug ferrule mounted upon an optical fiber of a fiber optic cable to at least one receptacle ferrule of like configuration mounted upon an optical fiber disposed in a receptacle within an enclosure when the plug is inserted into the receptacle, the plug further comprising: an outer housing defining an opening extending between first and second ends of the outer housing; an inner housing disposed within the outer housing; and an adapter sleeve for receiving the at least one plug ferrule disposed within the outer housing adjacent the inner housing.
 17. The fiber optic receptacle and plug assembly of claim 16, further comprising a coupling nut for securing the plug to the receptacle with the at least one plug ferrule in a predetermined orientation relative to the at least one receptacle ferrule.
 18. The fiber optic receptacle and plug assembly of claim 16, wherein the outer housing comprises a key for aligning the at least one plug ferrule in a predetermined orientation relative to the at least one receptacle ferrule.
 19. The fiber optic receptacle and plug assembly of claim 16, wherein the fiber optic cable is one of a branch cable, a distribution cable, an extended distribution cable, a flat dielectric drop cable, a figure-eight drop cable and an armored drop cable.
 20. The fiber optic receptacle and plug assembly of claim 16, wherein the at least one receptacle ferrule and the at least one plug ferrule are selected from the group consisting of SC, LC, MTRJ, MTP, SC-DC connector type ferrules. 